Water-Evaporation Supported Fuel Cell Cooling Architectures for Aircraft

This paper proposes to support ram air cooling of low and medium temperature fuel cells in aircrafts with additional water evaporation. This support should be designed as an extra cooling possibility and should be only used when required. This is especially during takeoff in hot ambient conditions. Water evaporation is for those conditions 50 to 100 times more efficient than air cooling, and the additional water evaporation system is expected to add comparatively little additional mass, since the resulting water vapor can be directly vented to the environment. However, the use of a water evaporation system allows a significant reduction in the size of the ram air cooling system, its mass and its drag, as the ram air system can be designed for cruise conditions. This paper introduces different architectures for integrating additional water evaporation systems in aircrafts and discusses their advantages and disadvantages at cooling system level, but also their impact on overall aircraft performance. The downsizing of the ram air channel and the eventual possibility to downsize buffer batteries is expected to have a large impact on the overall system weight.